LOW-TEMPERATURE DYEING ADDITIVE FOR PROTEIN FIBER PRODUCT

Abstract: A low-temperature dyeing additive for protein fiber products, which has a pH value of 3.5 to 9.5 and contains 0.025-40 g, per liter of water, of at least one solvent which has a donor number of 24 to 50 and an acceptor number of 10 to 24 in the presence or absence of a surfactant and is freely miscible with water. If necessary, the additive further contains 0.025-4.0 g of tributoxyethyl phosphate per liter of water and/or 0.05-40 g of at least one kind of anion having an enthalpy of hydration (-ΔH KJ.mol -1) of 200-290 per liter of water. This additive serves to relax the higher-order structures of the protein fibers before or after dyeing to thereby swell the fibers, thus rendering the fibers readily dyeable without detriment to the properties thereof.

Description: TECHNICAL FIELD This invention relates to a low-temperature dyeing process for protein fiber products made from wool, silk, etc. More specifically, it relates to a low-temperature dyeing process which is capable of dyeing protein fiber products at a temperature of not more than 90 °C. BACKGROUND ART Heretofore, dyeing of this kind of protein fiber products is generally carried out in an acidic dyeing bath at a boiling temperature. Thus, various troubles such as yellowing, shrinkage, lowering in strength of protein fiber, and difficulty in color matching due to yellowing, and the like are generated. Accordingly, the conventional protein fiber dyeing technique is not necessarily optimum in view of obtaining protein fiber products with high quality, high added value and low energy cost. On the other hand, in order to solve these problems, there has been investigated a low-temperature dyeing method comprising an easily dyeing treatment of protein fiber such as an ammonia pre-treatment, an enzyme pre-treatment, a 1-propanol treatment, an alkaline agent treatment, etc. However, this dyeing method at a low-temperature has not yet been practically used for the reasons mentioned below. That is, whereas the ammonia pre-treatment has been admitted as effective for obtaining an easily dyeing effect, various problems related to its volatility and irritating odor have occurred. Also, the oxygen pre-treatment is effective for easy dyeing, but according to the present situation, it requires high costs and involves problems in that dyeing fastness of the resulting dyed material is rather low and a generation ratio of dyeing unevenness is high. Further, the 1-propanol treatment involves the problem that a uniform effect can hardly be obtained unless a large amount of treating agent is used. Moreover, the alkaline agent treatment is effective for easy dyeing, but it involves the problem that a uniform effect cannot be obtained since the alkaline agent is too strong in a property as a donor. R. S. Asquith and A.K. Booth in Journal of the Society of Dyers and Colorists, Vol. 87 (1971), 334 to 337 describe investigations towards the rapid low-temperature dyeing of wool utilizing swelling and disaggregating agents selected from urea, dimethylformamide, cresol, formic acid, thioglycollic acid, and mixtures with water of dimethylformamide, methanol, n-propanol and isopropanol. Chemical Abstracts, Vol. 104 (1986), 131 340 z describes low-temperature dyeing of silk pretreated with organic solvents selected from ethylenediamine, α-picoline, benzylalcohol, pyridine, dimethyl sulfoxide and dimethylformamide. An object of the present invention is to provide a low-temperature dyeing process for protein fiber products, which serves to relax the high-order structures of the protein fibers before dyeing or during dyeing thereby swell the fibers without impairing physical properties thereof. Another object of the present invention is to provide a method of dyeing protein fiber products with high quality and high dyeing density without impairing physical properties thereof after treating or while treating the protein fibers with the low-temperature dyeing additive. DISCLOSURE OF THE INVENTION The invention relates to a process for the dyeing of protein fibers, wherein the fibers are subjected to pretreatment with a dyeing additive - containing aqueous bath and then subjected to dyeing at a temperature in the range of 70 to 90°C, wherein said bath has a pH of 3.5 to 9.5 and contains one or more solvents selected from dimethylformamide, N-methylpyrrolidone, N-dimethylacetamide, dimethylsulfoxide, N-diethylacetamide, N-methylmorpholine, pyridine and hexamethylphosphoric triamide in an amount of 0.025 to 40 g per liter of water, and one or more anions of salts selected from potassium thiocyanate, sodium thiocyanate, ammonium thiocyanate and sodium perchlorate in an amount of 0.05 to 40 g per liter of water. In a specific embodiment of the process of the present invention said bath further contains tributoxyethyl phosphate (TBXP) in an amount of 0.025 to 4.0 g per liter of water. The present invention will be explained in detail below. (a) Protein fiber products The protein fiber products to be dyed with the process of the present invention are animal hair fiber such as wool, cashmere, alpaca, etc., cocoon fiber obtained from cocoons of raised silkworm, wild silkworm, etc. or wool, silk made of these fibers, or fabric, knitting and nonwoven fabric made from these fibers or yarn. (b) Solvent The solvents used in the process of the present invention is a solvent which is freely miscible with water and has a donor number within the range of 24 to 50 and an acceptor number within the range of 10 to 24. Those solvents are selected from dimethylformamide, N-methylpyrrolidone, N-dimethylacetamide, dimethylsulfoxide (hereinafter referred to as "DMSO"), N-diethylacetamide, N-methylmorpholine (hereinafter referred to as "N-MM"), pyridine and hexamethylphosphoric triamide. If the donor number is less than 24, relaxation of a hydrogen bond of a protein fiber is insufficient. Contribution of the hydrogen bond is markedly large for the higher order structure of the protein fiber, so that it is necessary for the solvent to have a donor number of 24 or more to cut the hydrogen bond of the protein fiber and to solvate the protein fiber to the solvent whereby promoting diffusion and permeation of a dye therein. However, if the donor number exceeds 50, it is advantageous to cut the hydrogen bond but fixation of a dye is rather prevented. Also, if the acceptor number is less than 10, dyeing and fixation are too fast whereby uniform dyeing is impaired. If it exceeds 24, its proton donating property is too strong whereby a high effect of the donor number is decreased so that diffusion and permeation of a dye becomes rather insufficient. The concentration of the solvent to be used is from 0.025 to 40 g per liter of water and a high concentration gives a higher effect, but in view of an economical standpoint, the upper limit is 40 g. However, in a solvent which itself shows an alkaline property, i.e., a pH of 9.5 or higher, bad effects are exerted in dyeing behavior, and physical properties are lowered so that the maximum concentration to be used is determined within the range not exceeding a pH of 9. 5. In view of dyeing performance, the lower limit of the pH is 3.5. (c) Tributoxyethyl phosphate (TBXP) Heretofore, TBXP which is difficultly soluble in water is made soluble in water only by an emulsifier and a lower alcohol soluble in water so that there is a problem that a separation phenomenon is generated in a markedly diluted solution. To the contrary, in the present invention, it can be made self-emulsifiable without causing such problems by using a glycol ether which is soluble in water. Examples of water-soluble glycol ethers may include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, etc. The concentration of the TBXP to be used is from 0.025 to 4.0 g per liter of water, and a high concentration gives a higher effect, but in view of an economical standpoint, the upper limit is 4.0 g. (d) Anions of salts The anions of salts include anions (SCN - , CℓO 4 - ) and are selected from potassium thiocyanate, sodium thiocyanate, ammonium thiocyanote and sodium perchlorate, having a enthalpy of hydration (-ΔH KJ·mol -1 ) of 200 to 290. The concentration of the anions to be used is from 0.05 to 40 g per liter of water and a high concentration gives a higher effect, but in view of an economical standpoint, the upper limit is 40 g. (e) Surfactant The low-temperature dyeing additive-containing aqueous bath used in the process of the present invention is not necessarily required to contain a surfactant, but in view of permeating the additive to the protein fiber products rapidly, it is preferably contained. Examples of the surfactant may include nonionic surfactants such as ethylene oxide adducts of lauryl alcohol (added molar number: 3 to 6), and anionic surfactants such as alkylsulfosuccinate. These surfactants may be used singly or in combination. The concentration of the surfactant to be used is preferably 2 g or less per liter of water. (f) Treatment with the low-temperature dyeing additive and dyeing method In the treatment (pretreatment) of the protein fiber products with the low-temperature dyeing additive-containing bath and the dyeing of the treated protein fiber products, either methods of a two-bath method, a one-bath method or a simultaneous same-bath method may be used, and readily dyeable effect can be sufficiently accomplished. Among them, the one-bath method or the simultaneous same-bath method is preferred in view of economical standpoint and reproducibility. In the case of the two-bath method, a processing temperature is 40 to 60 °C and a processing time at the temperature is desirably 15 to 45 minutes. In the case of the one-bath method, a processing temperature is 40 to 60 °C which is the initiating temperature at dyeing, and a processing time at the temperature is preferably 5 to 30 minutes. Further, in the case of the simultaneous same-bath method, a processing initiating temperature is 35 to 40 °C, and a processing time is preferably an elevating time until a dyeing temperature of 70 to 90 °C. After the readily dyeable treatment (pretreatment) of the protein fiber products, the fiber products may be subjected to dyeing by the conventional protein fiber dyeing method, but they may be subjected to dyeing at a higher pH than the conventional method. By subjecting to dyeing at the higher pH, physical properties of the protein fiber products can be retained. In the two-bath method, the protein fiber products are processed (pretreated) in the first bath, and then the protein fiber products are dyed in the next bath. The first processing solution is simply removed as a waste solution and washing with water of the protein fiber products is not necessary. To wash the protein fiber products with water is not necessary since it decreases dyeing effects. After removing the first processing solution, a fresh solution which is capable of dyeing the protein fiber products is prepared. On the other hand, in the one-bath method, after completion of a readily dyeing treatment and after adding a dyeing solution containing a dye, an acid with a calculated amount which is suitable for acidification necessary for dyeing the protein fiber products is added to carry out dyeing, or an acid in a calculated amount which is suitable for acidification necessary for dyeing is added by dividing several times until completion of raising the temperature. Further, in the simultaneous same-bath method, it is preferred to add an acid in a calculated amount which is necessary for acidifying a dye for dyeing the protein fiber products, by dividing to several portions after 5 minutes from initiating the processing and until completion of raising the temperature. This is one of the characteristic features of the dyeing method of the present invention. After treating with the low-temperature dyeing additive-containing bath, or dyeing which is carried out while effecting the treatment, the higher-order structures of the protein fibers relax due to the above solvent. TBXP, anion, etc., whereby resistance to absorbing the dye is lowered to become readily dyeable. That is, the solvent promotes diffusion and permeation of the dye by cutting hydrogen bonds of the protein fibers or increasing affinity of the protein fibers to the solvent, but if the amount is too much, there is a risk of destroying the higher-order structures accompanied by dissolution of tissues. Accordingly, in order to make the amount of the solvent to be used as little as possible and to promote fixation of the dye, it is effective to add an anion having an enthalpy of hydration (-ΔH KJ·mol -1 ) of 200 to 290. If the enthalpy of hydration (-ΔH KJ·mol -1 ) is less than 200, cutting action against hydrogen bonds is little, while if it exceeds 290. fixation of the dye is hindered. Also, TBXP selectively shows affinity to a specific portion of higher-order structures of protein fibers such as a β phase of C.M.C of wool fiber and, by permeating and swelling, promotes formation of an inner passage in protein for a dye. At this time, the low-temperature dyeing process of the present invention maximally relaxes the higher-order structures of the protein fiber and does not destroy the higher-order structures. Thus, when the treated protein fiber products are dried, the higher-order structures are reconstituted. Therefore, there is little effect on the physical properties of the protein fiber and dyeing fastness is also good. According to the dyeing method of the present invention, as compared with the conventional boiling dyeing, low-temperature and short time dyeing of protein fibers are realized. This means that physical properties of the protein fibers are not lowered, yellowing of the same is prevented to simplify the color matching operation and to decrease a percentage of rejects of color matching. A dye which is used under strongly acidic conditions in the conventional and usual dyeing method is capable of dyeing under moderate acidic conditions in the dyeing method of the present invention. This means that low-temperature dyeing is realized as well as deterioration of physical properties such as yellowing, shrinkage, decrease in strength of the protein fibers can be prevented. When a high density dyeing is to be carried out, such a dye is incomplete in dissolution in a dyeing bath in the conventional method so that unevenness of dyeing is easily generated whereby a tendency of lowering in dyeing fastness is observed. This problem can be overcome in the dyeing method of the present invention. Also, dyeing fastness of the protein fiber products subjected to low-temperature dyeing according to the dyeing method of the present invention is the same or more as compared with protein fiber products obtained by subjected to boiling dyeing by the conventional strongly acidic dyeing bath. Further, in the fiber products obtained by low-temperature dyeing, yellowing of protein fiber is little so that the fiber shows a color hue inherently possessed by the dye and excellent color sharpness. BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a drawing showing a dyeing situation in an Example of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Next, examples of the present invention are explained with Comparative examples. Examples herein mentioned are not to be construed as limiting the technical range of the present invention. 1 ○ Preparation of DMSO 25 and DSA 6 for the first low-temperature dyeing additive A solvent of DMSO (produced by ASAHI CHEMICAL CO., LTD.) with a ratio of 250 g per liter of water was dissolved to prepare an aqueous solution (hereinafter referred to as DMSO 25 ). Furthermore 300 g of dioctyl·sulfo·sodium succinate as a surfactant, 50 g of diethylene glycol dimethyl ether and 50 g of isopropanol were mixed with one liter of water. This surfactant composition is hereinafter called DSA 6 . 2 ○ Preparation of N-MM 25 for the first low-temperature dyeing additive In the same manner as in the above 1 ○ except for using 250 g of a solvent N-MM (produced by KISHIDA CHEMICAL CO., LTD.) in place of DMSO, an aqueous N-MM solution was prepared, hereinafter called N-MM 25 . 3 ○ Preparation of a TBXP self emulsified solution for the second low-temperature dyeing additive 20 % by weight of TBXP, 40 % by weight of methanol, 7 % by weight of diethylene glycol monomethyl ether, 7 % by weight of polyoxyethylenephenyl ether and 26 % by weight of water were uniformly mixed to prepare a TBXP self-emulsified solution (hereinafter called TBXP s ). 4 ○ Preparation of anion solution NH 4 SCN 25 for the third low-temperature dyeing additive An anion of SCN - (an enthalpy of hydration (-ΔH KJ·mol -1 ) of 290) of ammonium thiocyanate <produced by NIHON KAGAKU SAN-GYO CO., LTD.) was mixed with one liter of water with a ratio of 250 g to prepare an anion solution No. 1 (hereinafter called NH 4 SCN 25 ). 5 ○ Preparation of anion solution (NaClO 4 ) 25 for the third low-temperature dyeing additive An anion of CℓO 4 - (an enthalpy of hydration (-ΔH KJ·mol -1 ) of 200) of sodium perchlorate (anhydride) (produced by KISHIDA CHEMICAL CO., LTD.) was mixed with one liter of water with a ratio of 250 g to prepare an anion solution No. 2 (hereinafter called to as (NaCℓO 4 ) 25 ). <Examples 1 to 19> A low-temperature dyeing treatment and dyeing were carried out with a two bath method. That is. plain fabrics muslin woolen cloth with the woof of No. 1/60 meter x 14/cm and the warp of No. 1/60 meter x 14/cm was prepared. In a minicolor dyeing tester (manufactured by TEXAM CO.. LTD.), the woolen cloth and a low-temperature dyeing additive with a prescription as shown in Table 1 below with a bath ratio of 1:25 were charged, and treatment was effected at 40 °C for 30 minutes (first bath). Next, the treating solution was discharged from the dyeing tester. Thereafter, the treated woolen cloth was dyed in a second bath (water with dissolved dye 1 %owf of a leveling acidic dye (Telon Blue K BRLL) and formic acid with a bath ratio of 1:25), and the temperature of the bath was raised from 40 °C to 85 °C with the rate of 1.5 °C/minute, and dyeing occurred at 85 °C for 40 minutes to adsorb the dye. After dyeing, the woolen cloth was taken out from the dyeing tester, washed with water and dried to obtain a uniform blue colored cloth. Then the pH of the residual bath was measured by pH. Meter. F. 8E (manufactured by HORIBA LTD.) to obtain a value as shown in Table 1. Further, by using Ubest-30 Type Spectrophotometer (manufactured by JAPAN SPECTROSCOPIC CO., LTD.). an absorbance (hereinafter called to as DEH-1) of the first bath dyeing solution and an absorbance (hereinafter called to as DEH-2) of the dyeing solution after completion of dyeing were measured. respectively, and a dye absorption ratio (hereinafter called to as DEH) was measured by the following equation to obtain the value shown in Table 1. Dye absorption ratio (%) = {(DEH-1 - DEH-2)/DEH-1} x 100 DMSO 25 (g/l) N-MM 25 (g/l) TBXP s (g/l) NH 4 SCN 25 (g/l) NaCℓO 4-25 (g/l) DSA 6 (g/l) DEH (%) pH Example 1 0.1 - - - - 3.0 99 4.0 Example 2 3.0 - - - - 3.0 99 4.0 Example 3 - 0.1 - - - 3.0 99 4.0 Example 4 - 3.0 - - - 3.0 99 4.0 Example 5 - 10.0 - - - 3.0 99 4.0 Example 6 1.5 - 1.3 - - 3.0 99 4.2 Example 7 - 2.0 1.3 - - 3.0 99 4.2 Example 8 1.5 2.0 - - - 3.0 99 4.2 Example 9 1.5 - - 1.0 - 3.0 99 4.2 Example 10 1.5 - - - 1.0 3.0 99 4.2 Example 11 1.5 2.0 1.3 - - 3.0 99 4.2 Example 12 1.5 - 1.3 1.0 - 3.0 99 4.2 Example 13 1.5 - 1.3 - 1.0 3.0 99 4.2 Example 14 - 2.0 1.3 1.0 - 3.0 99 4.2 Example 15 - 2.0 1.3 - 1.0 3.0 99 4.2 Example 16 1.5 2.0 - 1.0 - 3.0 99 4.2 Example 17 1.5 2.0 - - 1.0 3.0 99 4.2 Example 18 1.5 2.0 1.3 1.0 - 3.0 99 4.2 Example 19 1.5 2.0 1.3 - 1.0 3.0 99 4.2 To the contrary, DEH of non-treated muslin woolen cloth, i.e. not treated with the low-temperature dyeing additive of the present invention was only 85 %. Furthermore the same muslin woolen cloth used in Examples 1 to 19 was subjected to boiling dyeing at a pH of the sulfuric acid-acidic bath of 2.5 at 100 °C for 60 minutes, and friction fastness, washing fastness, sweat fastness and light-resistant fastness were determined as compared to the cloth dyed in Examples 1 to 19. The results are that the respective fastnesses of the muslin woolen clothes dyed in Examples 1 to 19 were the same as those of muslin clothes subjected to boiling dyeing. <Examples 20 to 38> Low-temperature dyeing treatment and dyeing were carried out by the one bath method. That is, the same muslin woolen clothes as used in Examples 1 to 19 were treated with the low-temperature dyeing additives having prescriptions shown in Table 1 in the same manner as in Examples 1 to 19. Without discharging this treating solution from the dyeing tester, the same dye as in Examples 1 to 19 and formic acid were added to the treating solution to make the dyeing bath pH 3. 8, and dyeing was carried out in the same manner as in Examples 1 to 19 to obtain uniform blue colored dyeing clothes. DEH of the remaining bath was 98.5 % or more and the pH of the remaining bath was 4. 2. The fastnesses of the muslin woolen clothes obtained were the same as those of Examples 1 to 19. <Example 39> Low-temperature dyeing treatment and dyeing were carried out by the simultaneous same-bath method. That is, after charging the low-temperature dyeing additive having a prescription shown in Table 2 and the same dye as in Examples 1 to 19 in a dyeing tester, the same muslin woolen cloth as used in Examples 1 to 19 was also charged in the dyeing tester and swelled sufficiently in the dyeing solution at 40 °C for 5 minutes. Then, the temperature was raised from 40 °C to 85 °C at a rate of 1. 5 °C/minute, and during the temperature raising formic acid was added to the dyeing solution dividing into 5 times. Dyeing was carried out at 85 °C for 40 minutes to adsorb the dye. The situation is shown in Fig. 1. After dyeing the woolen cloth was taken out from the dyeing tester, washed with water and dried to obtain a uniformly blue colored cloth. DEH of the remaining bath was 98.5% or more, and the pH of the remaining bath was 4.2. Friction fastness, washing fastness, sweat fastness and light-resistant fastness of the muslin woolen cloth dyed by this dyeing method were not less than the respective fastnesses of muslin woolen cloth subjected to boiling dyeing at a pH of the sulfuric acid-acidic bath of 2.5 at 100 °C for 60 minutes. DMSO 25 (g/l) N-MM 25 (g/l) TBXP s (g/l) NH 4 SCN 25 (g/l) NaCℓO 4-25 (g/l) DSA 6 (g/l) DEH (%) pH Example 39 1.5 2.0 1.25 1.0 1.0 3.0 98.5 4. 2 <Examples 40 to 78> Examples 1 to 39 were repeated except for changing the dye used in Examples 1 to 39 to a chromium dye (C. I. Mordant Black) and adding the dye with 3 %owf. After adsorbing the dye at 85 °C for 40 minutes, 0.6 %owf of sodium bichromate was added, and chromating treatment was carried out at 85 °C for 40 minutes. Muslin woolen clothes dyed to a uniform black color were obtained. DEH of the remaining bath immediately before addition of sodium bichromate was 95.4 %, and the pH of the acidic bath was 4.2. Friction fastness, washing fastness, sweat fastness and light-resistant fastness of the obtained muslin woolen clothes were completely the same as the respective fastnesses of muslin woolen cloth subjected to boiling dyeing at 97 °C for 60 minutes. As described above, according to the low-temperature dyeing method for the protein fiber products of the present invention, there are characteristics that it serves to relax the higher-order structures of the protein fibers before dyeing or during dyeing and swelling the fiber without impairing the excellent properties possessed by the protein fiber. By subjecting to dyeing at a relatively low temperature within a short time by using the low-temperature dyeing method with pretreatment, protein fiber products can be dyed with good reproducibility without impairing the physical properties thereof with a low dyeing cost and a high dyeing density. As the results, various problems such as yellowing. shrinkage and lowering in strength of protein fibers or difficulty in color matching which are problems involved in the conventional acidic boiling dyeing method of protein fiber products, or various problems involved in readily dyeing due to an ammonia pre-treatment or an enzyme pre-treatment or readily dyeing due to a 1-propanol treatment or an alkaline agent treatment can be solved at a stroke. Thus, protein fiber products having high quality and high added value can be produced readily with low energy. Particularly, introduction of a low-temperature and short time dyeing method according to the present invention leads to energy reduction in dyeing processing, and a dye adsorbing ratio is extremely high so that a degree of pollution due to a dyeing solution discharged is low which contribute to prevent worsening the earth environment. INDUSTRIAL APPLICABILITY The low-temperature dyeing additive of the protein fiber products of the present invention is available for readily dyeing without impairing physical properties of fibers.

Claims: A process for the dyeing of protein fibers, wherein the fibers are subjected to pretreatment with a dyeing additive - containing aqueous bath and then subjected to dyeing at a temperature in the range of 70 to 90°C, wherein said bath has a pH of 3.5 to 9.5 and contains one or more solvents selected from dimethylformamide, N-methylpyrrolidone, N-dimethylacetamide, dimethylsulfoxide, N-diethylacetamide, N-methylmorpholine, pyridine and hexamethylphosphoric triamide in an amount of 0.025 to 40 g per liter of water, and one or more anions of salts selected from potassium thiocyanate, sodium thiocyanate, ammonium thiocyanate and sodium perchlorate in an amount of 0.05 to 40 g per liter of water. The process of claim 1, wherein said bath further contains tributoxyethyl phosphate in an amount of 0.025 to 4.0 g per liter of water.

Inventors: KOIKE SACHIZUMI, KOIKE, SACHIZUMI
Applicants: TUYAKU CO LTD, TUYAKU CO., LTD.
Application year: 1994
Main classification: D06P5
IPC codes: D06P5, D06P1, D06P3